One embodiment relates to an apparatus and method for providing relief and/or reinforcement to a hydraulic choke valve from exposure to excessive backpressure. More particularly, one embodiment relates to pressure reducing valves and valve openings having secondary reinforcing members.
One embodiment can be applicable to hydraulic choke valves, which are a subclass of pressure reducing valves. Choke type pressure reducing valves generally function by causing a portion of the potential energy of a pressurized fluid to be dissipated through turbulence when the pressurized fluid is passed through a restrictive orifice. Typically, the orifice of a choke valve is selectably variable through reciprocation of its valving member toward and away from the valve seat, so that a desired combination of flow and exit pressure may be obtained.
A choke valve is normally open and is designed for one-way flow. This construction differs from that of a relief valve, which is another type of one-way flow valve that is normally closed. The present invention is applicable to a choke valve that differs in construction from the most common arrangement of such valves in having its flow gate pressure-balanced. Because of the pressure balancing of the sealing plug, the actuating loads on the stem of the flow gate are considerably reduced compared to those of most choke valves of comparable capacity. However, the stem of the flow gate, which connects to the reciprocable control screw of the actuator used to reciprocate the flow gate for this type of choke, is not pressure balanced causing possibly substantially increased loading on such stems and the housings supporting such stems.
In one embodiment excessive axial loading is reinforced and/or assumed by a detachably connectable reinforcing member which is attached to the primary housing of the valve body.
Excessive axial loading on valve plugs has been addressed using shearable relief means of opening a relief valves on single time basis using a shearing member which must be repaired after a shearing event. Schmidt et al. U.S. Pat. No. 7,124,770 discloses a mechanism for preventing damage to the actuator of a hydraulic choke valve in the event of excessive backpressure on the outlet of the choke which uses a shearable means to connect the reciprocable control shank of the actuator to the throttling valve member of the choke valve where in the event of excessive pressure on the exit channel of the choke valve, the shearable means will shear, thereby fully opening the valve and permitting the excessive pressure to escape. However, each time the shearing means is used, the valve must be taken out of commission so that the shearing means can be replaced.
The above prior art solution require modifications to the stems and actuators, along with rebuilding same after failure necessitating taking the valves with such solutions out of service in the event of a failure.